In order to splice two textile yarns it is possible to make a knot, which produces a firm but visible joint. A knotless joint can also be made by various methods. Such a joint is less visible than a knot but generally weakens the yarn. The ideal solution involves recreating the conditions of initial twist in the yarn as proposed, for example, in U.S. Pat. No. 2,362,801 or U.S. Pat. No. 3,903,680. The latter patent discloses that, in order to obtain a very strong joint, the fibers at the two ends to be joined should have previously been spread apart so that they can interpenetrate before being subjected to a twist. If the two ends are merely twisted together without prior interpenetration of the fibers, the joint is extremely weak since the two fiber bundles are wound helically around each other, the majority of the fibers therefore not contributing to the strength of the joint.
In order to obtain a bundle of spaced-apart fibers at an extremity of a first yarn capable of interpenetration with another bundle of fibers formed in the same manner at an extremity of a second yarn to be joined thereto, it is sufficient to untwist each of these extremities and to arrange the separated fibers in parallel. However, a separation of the fibers by simple untwisting is possible only with a yarn obtained by ring spinning. On the other hand, it is not possible to proceed in this way with yarns obtained by the so-called open-end spinning method or with ply yarns. In the first case, the fibers do not form more or less parallel and regular helices but are far less well ordered with some extending longitudinally while others are coiled. Consequently, mere untwisting is not sufficient to unravel a portion of such a yarn since the fibers are not all twisted together. In a ply yarn, the plies have to be unraveled first of all and then each yarn has to be unraveled, the ply twist and the twist of the yarns being in opposing directions.
It has consequently been found that the method according to U.S. Pat. No. 3,903,680 is not suitable for all types of yarn and that it can be carried out only if it is possible to unravel the fibers by a method other than untwisting.